This invention relates in general to solid tires for vehicles, and more particularly to an apparatus and process for removing such tires from the wheels on which they are installed.
The wheels of lift trucks and similar industrial vehicles are normally provided with solid rubber tires instead of pneumatic tires, as are most other automotive vehicles, and these tires consist of nothing more than a metal rim and a solid rubber tread bonded to the rim. The tire fits over the outside surface of the wheel and in order to achieve a secure mounting, the inside diameter of the rim must be small enough to provide an interference fit between the rim and the wheel. Hence, the tire is secured to the wheel by nothing than the friction of the interference fit. Installation of the tire on the wheel requires a heavy press, but the procedure itself is relatively simple. Usually a lubricant is spread over the inside surface of the rim to reduce the force necessary to press the tire in place.
Of course, the tread of the tire wears down during use, and it is also not uncommon for the tread to acquire large nicks, gouges, and cuts along its side edges as a result of the vehicle coming against sharp metal objects, curbs, and the like. In time, the tread wears out, requiring replacement of the complete tire.
Removing a worn tire from its wheel is not nearly so easy as installing a new tire over the same wheel. The common procedure likewise involves the use of a press, but normally the force required to press the tire off the rim is substantially greater than that necessary for installing the tire. For example, where a 40 ton press is often adequate for installing a tire, a 100 ton press is normally required to remove the tire, and often a press of that size is inadequate. The difficulty derives from the fact that oxidation of both the wheel and rim occurs at the interface between the two and this oxidation in effect unites the wheel and the rim of the tire. Also impacts between the rim and hard objects during use not only damage the side of the tire, but further peen the end edge of the rim slightly over the end of the wheel, thereby compounding the removal problem. The problem is particularly acute in the case of large diameter wheels and so called dual wheels, which are twice the width of conventional wheels.
When the presses at a repair shop prove inadequate, the shop normally locates an even larger press at some other location for removing the tire. This can often be inconvenient. Another alternative is to burn the tire off of the rim, and then sever the rim so that it falls off of the wheel. Usually an oxy-acetylene cutting torch is used for this purpose. The flame from the torch is first applied to the rubber tread to burn a groove completely across the tread, and this groove is deep enough to expose the metal of the rim. However, the thick rubber does not burn rapidly and when it does large amounts of dense black smoke are produced. It is not uncommon to require at least an hour of burning to provide a suitable groove in the tread. Once the groove is finished, the steel rim, which is typically about 1/4 inch thick, is cut through the base of the groove.